Motion Sensitive Video Watermarking final report

The aim of this project is to remove the motion related artifacts of the current watermarking algorithm, known as the ‘dirty window problem’. It was observed that part of the dirty window problem originated from watermark artifacts in still images. Therefore, two possible improvements of the current algorithm are suggested that will lower the visibility of the watermark in still images: adjusting the global depth settings of the four directional watermark patterns, and changing the fixed clipping threshold to a clipping threshold that depends on the luminance value of a pixel. The following model for a motion sensitive watermarking algorithm is proposed, and has subsequently been implemented: 1. use the current algorithm to calculate a watermark for a frame; 2. select areas in the frame that might expose the watermark when they are in motion; 3. estimate the motion in the frame; 4. lower the local strength of the watermark in selected areas that are in motion. In step 2, areas are selected based on the output of the directional filters. In step 3, the Y-prediction block-matcher is used to extract motion information from a video sequence. Finally, a number of improved watermarking algorithms were evaluated in a visibility test, and the robustness of the algorithms to MPEG-2 compression was determined. Conclusions: The improved global depth settings successfully lower the visibility of the watermark, at virtually no change in the robustness of the watermark. Employing motion compensation lowers the visibility of the watermark, at a small decrease of watermark robustness. Adding soft luminance clipping improves the invisibility of the watermark, but seriously degrades watermark robustness. Simultaneously applying motion compensation and the improved global depth settings is the most promising improvement of the invisibility of the watermark. It is expected that the cumulative effect of motion compensation and the improved depth settings will give a significant improvement in watermark invisibility, with only a marginal loss of watermark detectability. c ©Philips Electronics N.V. 2001 iii 2001/825 no classification iv c ©Philips Electronics N.V. 2001